JP7102738B2 - Evaluation method for pipe expansion, mold for pipe expansion evaluation, evaluation pipe for pipe expansion - Google Patents

Description

The present invention relates to a method for evaluating pipe expansion, a mold for evaluating pipe expansion, particularly a split mold constituting the mold, and an evaluation pipe for pipe expansion.

In conventional wells, a casing with several stages of pipe diameter depending on the geology is formed by inserting an oil well pipe connected with a screw immediately after excavation, cementing it, and repeating the process of passing a pipe with a smaller diameter inside it. Design and construct. For this reason, the oil well pipe near the ground has a large diameter and the laying cost is high, and the pipe diameter is gradually reduced as the depth increases, so that there is a limit to the depth of the oil well. Therefore, in recent years, an expansion type oil well pipe has been developed that is used by expanding the pipe by about 10 to 30% in the oil well. By using this, the difference in pipe diameter of the entire well can be reduced, and the laying cost can be reduced and the depth of the well can be increased.

Such an expansion type oil well pipe is required not to break even if it is expanded to a predetermined size. To confirm this, it was necessary to prove that it did not break in a full-scale pipe expansion test that reproduces the pipe expansion in the oil well. In addition, due to changes in user safety awareness, external flaws that may occur while transporting the well pipe from the manufacturing plant to the well site, and hard and sharp rocks in the ground when inserting the pipe into the well, etc. A tube expansion evaluation may also be conducted assuming that the outer surface will be scratched. In this case, an artificial defect is provided on the outer surface of the pipe by machining to perform a full-scale pipe expansion test. Therefore, in the full-scale tube expansion test, a test as described in Patent Document 1 was performed.

Japanese Unexamined Patent Publication No. 2009-222652

However, it takes two to three months to manufacture a full-scale tube expansion test piece, and it costs several million yen per piece, so rapid evaluation such as shipping test cannot be performed. Therefore, the development of a simple evaluation method for pipe expansion is required. Therefore, the present inventor has developed a simple tube expansion evaluation method in which an artificial defect is provided in an evaluation tube smaller than a full-scale tube expansion.

The present invention is an invention made in such a background, and an object of the present invention is to enable a simple evaluation of a flawed tube expansion using an evaluation tube.

In order to solve the above problem, when the strain history is acquired from the numerical analysis of full-scale tube expansion or the tube expansion experiment, and the core metal that extrudes the split mold placed in the evaluation tube with artificial defects in the radial direction of the evaluation tube is used. In addition, the stroke of the core metal whose circumferential strain of the evaluation part of the evaluation tube is equivalent to that of full-scale tube expansion and whose axial strain is within the range of ± 1.5% of axial strain of full-scale tube expansion is derived and derived. A full scale corresponding to the evaluation tube is formed by moving the core metal within the stroke range and extruding the split mold to form an expanded evaluation tube, and checking the condition around the artificial defect of the expanded evaluation tube. It is an evaluation method of pipe expansion, which is characterized by judging the quality of pipe expansion. The circumferential strain of the evaluation section of the evaluation tube is equivalent to that of the full-scale expansion tube, which means that the circumferential strain of the evaluation section of the evaluation tube is within the range of ± 1.0% of the circumferential strain of the full-scale tube expansion. ..

Further, the split type satisfies 4.0 ≦ R / t ≦ 12.0 and 0.05 ≦ μ ≦ 0.15, and the evaluation tube satisfies 3.0 ≦ L / t ≦ 30.0. It is preferable that 0.1 ≦ l / L ≦ 0.5 is satisfied. (However, R: split surface radius [mm], t: evaluation tube wall thickness [mm], μ: friction coefficient of split surface, L: evaluation tube length [mm], l: artificial defect length [mm ])

In addition, it will be a split type for tube expansion evaluation that meets the following conditions.
4.0 ≤ R / t ≤ 12.0, 0.05 ≤ μ ≤ 0.15 (However, R: split surface radius [mm], t: evaluation tube wall thickness [mm], μ: split surface Friction coefficient)

In addition, the evaluation tube for expansion that satisfies the following conditions shall be used.
3.0 ≤ L / t ≤ 30.0, 0.1 ≤ l / L ≤ 0.5 (where L: evaluation tube length [mm], t: evaluation tube wall thickness [mm], l: artificial defect Length [mm])

According to the present invention, it is possible to perform a simple evaluation of a flawed tube expansion using an evaluation tube.

It is a perspective view which showed the core metal, the split type and the evaluation tube at the time of expanding the evaluation tube. It is sectional drawing which showed the core metal, the split mold and the evaluation tube at the time of expanding the evaluation tube. It is sectional drawing which showed the state before and after expanding the evaluation tube using a core metal and a split mold. However, the state before the pipe expansion is shown at the uppermost part, and the state where the pipe is expanded toward the lower side is shown in order. It is a partially enlarged view of the IV-IV cross section of FIG. It is a figure showing the state of full-scale tube expansion using a tube expansion plug. It is the figure which showed the state which flared tube is expanded using the mold. It is a figure which shows the relationship between the axial strain and the circumferential strain of the full-scale tube expansion, flare tube expansion, and tube expansion of the present invention provided with flaws which are linear grooves.

A mode for carrying out the invention is shown below. In the evaluation method of tube expansion of the embodiment, the strain history is acquired from the numerical analysis of the full-scale tube expansion 6 or the tube expansion experiment, and the split mold 2 arranged in the evaluation tube 4 provided with the artificial defect 5 is placed in the radial direction of the evaluation tube 4. When the core metal 3 extruded to is used, the circumferential strain of the evaluation part of the evaluation tube 4 is equivalent to that of the full-scale tube expansion, and the axial strain is within the range of ± 1.5% of the axial strain of the full-scale tube expansion. The stroke of the core metal 3 is derived, the core metal 3 is moved within the range of the derived stroke, and the split mold 2 is extruded to form the expanded evaluation tube 4, and the artificial defect 5 of the expanded evaluation tube 4 is formed. By checking the surrounding state, the quality of the full-scale tube expansion 6 corresponding to the evaluation tube 4 is judged. Therefore, the evaluation tube 4 can be used to perform a simple evaluation of a tube expansion provided with a flaw.

At this time, it is assumed that the circumferential strain of the evaluation part of the evaluation tube 4 is equivalent to that of the full-scale tube expansion, and the axial strain is within the range of the axial strain of the full-scale tube expansion of ± 1.5%. This is because if it exceeds this range, it cannot be said that the difference between the fracture phenomenon caused by the split mold 2 to the evaluation tube 4 and the fracture phenomenon caused by the expansion plug 61 to the full-scale expansion tube 6 is sufficiently small. Numerical analysis is preferably used to derive strokes that fall within this range.

As can be understood from FIGS. 1 to 4, in this evaluation method, the evaluation tube 4 provided with the artificial defect 5 which is an artificial defect is used to expand the tube. The full-scale pipe expansion 6 may have a defect in the pipe expansion for some reason during transportation or installation. As for the full-scale pipe expansion 6, it can be said that the use environment is harsher than the state without the flaw because the state with the flaw is more likely to be an obstacle when the pipe is expanded. , The evaluation tube 4 can be used to determine whether or not the full-scale tube expansion 6 can cope with such a severe condition.

The split mold 2 of the embodiment is provided with a surface having an arcuate cross-sectional view so that the curved surface abuts on the inner peripheral side of the evaluation tube 4. The portion of the evaluation tube 4 provided with the artificial defect 5 is thinner than the portion around the artificial defect 5, but the split mold 2 is used to push out from the inside of the thinned portion. ..

The tip of the core metal 3 of the embodiment has a cone trapezoidal shape, and by fitting it between the split molds 2, the split molds 2 arranged in a circular shape expand at least a part of the evaluation tube 4 in the radial direction. Can be done.

In the present invention, the split mold 2 plays an important role, but by diligently examining the split mold 2, it was found that there are favorable conditions. It is 4.0 ≦ R / t ≦ 12.0, 0.05 ≦ μ ≦ 0.15 (however, R: split surface radius [mm], t: wall thickness of evaluation tube [mm], μ: split The condition of the friction coefficient of the mold surface) is satisfied (see FIG. 2).

The reason why 4.0 ≦ R / t ≦ 12.0 is preferable is as follows. That is, when R / t, which is the value obtained by dividing the surface radius of the split die 2 by the wall thickness of the evaluation tube 4, is less than 4.0, the force of the split die 2 to restrain the axial direction of the evaluation tube 4 becomes excessive. This is because there is a risk that the axial strain will not fall within the appropriate range. Further, when R / t exceeds 12.0, the force of the split mold 2 to restrain the evaluation tube 4 in the axial direction becomes too small, and the axial strain may not fall within an appropriate range.

The reason why 0.05 ≦ μ ≦ 0.15 is preferable is as follows. That is, when μ, which is the coefficient of friction on the surface of the split mold 2, is less than 0.05, the force with which the split mold 2 restrains the evaluation tube 4 in the axial direction becomes too small, and the axial strain may not fall within an appropriate range. Because there is. Further, when μ exceeds 0.15, the force of the split mold 2 to restrain the evaluation tube 4 in the axial direction becomes excessive, and the axial strain may not fall within an appropriate range.

Further, in the present invention, the artificial defect 5 provided in the evaluation tube 4 plays an important role, but by diligently examining the artificial defect 5, it was found that there are preferable conditions. It is 3.0 ≦ L / t ≦ 30.0, 0.1 ≦ l / L ≦ 0.5 (where L: evaluation tube length [mm], t: evaluation tube wall thickness [mm], l: The condition of the artificial defect length [mm]) is satisfied (see FIG. 2).

The reason why 3.0 ≦ L / t ≦ 30.0 is preferable is as follows. That is, when L / t, which is the value obtained by dividing the length of the evaluation tube 4 by the wall thickness of the evaluation tube 4, is less than 3.0, the stress distribution under load is different from that of the full-scale expansion tube 6, and the axial strain is high. This is because there is a risk that it will not fall within the appropriate range. Further, when L / t exceeds 30.0, the force of the split mold 2 to restrain the evaluation tube 4 in the axial direction becomes excessive, and the axial strain may not fall within an appropriate range.

The reason why 0.1 ≦ l / L ≦ 0.5 is preferable is as follows. That is, when l / L, which is the value obtained by dividing the length of the artificial defect 5 by the length of the evaluation tube 4, is less than 0.1, the force of the split mold 2 to restrain the axial direction of the evaluation tube 4 becomes excessive. This is because there is a risk that the axial strain will not fall within the appropriate range. Further, when l / L exceeds 0.5, the force of the split mold 2 to restrain the evaluation tube 4 in the axial direction becomes too small, and the axial strain may not fall within an appropriate range.

Here, the evaluation section of the evaluation tube 4 in which the tube was expanded according to the present invention as shown in FIG. 1, the full-scale tube expansion 6 formed by using the tube expansion plug 61 as shown in FIG. 5, and as shown in FIG. FIG. 7 shows the relationship between the axial strain and the circumferential strain caused by the flare expansion tube 7 formed by the conical mold 71. As shown in FIG. 7, it can be seen that in the case of the flare tube expansion 7, the axial compression strain is considerably larger than that of the full-scale tube expansion 6 having the same circumferential strain. That is, it can be seen that the flare tube expansion 7 is inappropriate for simulating the full-scale tube expansion 6. On the other hand, if the method of the present invention is adopted, it can be seen that the strain is closer to the full-scale tube expansion 6 than the flare tube expansion 7. As shown in FIG. 4, the evaluation portion of the evaluation tube 4 referred to here is a corner portion of a recess provided near the center of the longitudinal axis of the artificial defect 5.

Further, the split mold 2 may be used as a set of two or more to push out the evaluation tube 4, but it is preferable that six to eight split molds 2 are arranged in a ring shape and used as a set.

Next, an example will be described. An experiment was conducted using an evaluation tube 4 having an outer diameter of 150.0 mm to 350.0 mm and a length of 25.0 mm to 610.0 mm. Further, the evaluation was performed by changing the conditions such as the length of the artificial defect 5 provided as the linear groove and the friction coefficient of the split mold 2. Further, the core metal 3 was pushed to the stroke value derived by the numerical analysis. The results are shown in Table 1.

By using the evaluation method of the present invention, the evaluation part of the evaluation tube 4 is observed, and whether or not there is a through crack, a constriction, or a surface surface is observed, and the quality is judged. By doing so, the full-scale tube expansion 6 can be evaluated.

Although the present invention has been described above focusing on the embodiments, the present invention is not limited to the above-described embodiments, and various aspects can be used.

20% type 3 core metal 4 evaluation tube 5 artificial defect 6 full scale tube expansion 7 flare tube expansion 61 tube expansion plug 71 mold

Claims (3)

Obtain strain history from numerical analysis of full-scale tube expansion or tube expansion experiment,
When a core metal that extrudes a split mold placed in the evaluation tube with artificial defects in the radial direction of the evaluation tube is used, the circumferential strain of the evaluation part of the evaluation tube is equivalent to that of full-scale tube expansion, and the axial strain is Derived the stroke of the core metal within the range of ± 1.5% of the axial strain of the full-scale tube expansion.
By moving the core metal within the range of the derived stroke and extruding the split mold, an expanded evaluation tube is formed.
An evaluation method for expanding a tube, which comprises checking the condition around an artificial defect of the expanded evaluation tube to judge the quality of the full-scale tube expansion corresponding to the evaluation tube.
here,
The split mold has a curved surface having an arcuate cross-sectional view that can abut on the inner peripheral side of the evaluation tube, and
4.0 ≤ R / t ≤ 12.0
0.05 ≤ μ ≤ 0.15
To meet
The evaluation tube has a groove-like artificial defect provided as a linear groove so as to be thinner than the surrounding part, and also has a groove-like artificial defect.
3.0 ≤ L / t ≤ 30.0
0.1 ≤ l / L ≤ 0.5
It satisfies .
(However, R: split surface radius [mm], t: evaluation tube wall thickness [mm], μ: friction coefficient of split surface, L: evaluation tube length [mm], l: artificial defect length [mm ]) A split type for tube expansion evaluation used in the method for evaluating tube expansion according to claim 1, wherein the following conditions are satisfied.
4.0 ≤ R / t ≤ 12.0
0.05 ≤ μ ≤ 0.15
(However, R: radius of the split surface [mm], t: wall thickness of the evaluation tube [mm], μ: friction coefficient of the surface of the split surface) An evaluation tube for tube expansion used in the method for evaluating tube expansion according to claim 1, wherein the following conditions are satisfied.
3.0 ≤ L / t ≤ 30.0
0.1 ≤ l / L ≤ 0.5
(However, L: evaluation tube length [mm], t: evaluation tube wall thickness [mm], l: artificial defect length [mm])

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